The present disclosure relates to an imaging member having a heat sensitive material whose surface compatibility to printing agents, such as toners and inks, can be substantially changed in response to a small variation in temperature. For example, a hydrophobic area of the surface of an imaging member can be quickly switched to a hydrophilic area upon exposure to a temperature shift. Similarly, an oleophilic area of the surface of the imaging member can be switched to an oleophobic surface. This disclosure also relates to apparatuses including such imaging members, and methods of using such imaging members, such as in lithographic printing applications.
Lithography is a method for printing using a generally smooth surface. The surface, such as the surface of a plate or of an imaging member, is comprised of (i) hydrophobic areas that repel solution (water) and attract ink; and (ii) hydrophilic areas that repel ink and attract solution. Fountain solution, which is typically a water-based solution, is then applied to the surface and adheres to the hydrophilic (i.e. oleophobic) areas while the ink adheres to the hydrophobic (i.e. oleophilic) areas to form the image.
In offset lithography, the image on the imaging member is generally then transferred to an intermediate transfer member which picks up the ink. The ink image on the intermediate transfer member is then transferred to the final substrate (e.g. paper).
Offset lithography offers consistent high image quality, large substrate latitude, and longer printing plate life compared to direct lithography processes. In addition, offset lithography generally offers lower costs for large-quantity duplicated printing because most of the cost in offset lithography is incurred upfront.
Conventional lithography techniques use an image plate with permanent hydrophobic areas and hydrophilic areas. However, such plates are costly and require considerable set-up time. This limits the attractiveness of lithography for short-run printings (i.e. low quantity) and variable-data printings (e.g. direct mail ads).
One approach has been to utilize heat-sensitive materials on the plate or imaging member to enable digital variable-data printing. However, such materials generally require high temperatures (e.g. greater than 100° C.) and/or are slow to reverse their state. It would be desirable to provide devices and/or methods for lithography where hydrophilic/hydrophobic states, etc., could be quickly changed by small temperature changes.